Soon, American men will have more than just Viagra to choose from for the treatment of erectile dysfunction (ED).

Bayer AG (NYSE:BAY) and GlaxoSmithKline (NYSE:GSK) announced last night that the FDA has approved Levitra (pronounced luh-VEE-trah) for the treatment of erectile dysfunction, and the new prescription drug should be available nationwide in a few weeks. What's more, Eli Lilly (NYSE:LLY) and Icos (NASDAQ:ICOS) are expected to gain approval for the impotence pill Cialis (pronounced see-ALL-iss) in the U.S. later this year. Both Cialis and Levitra have already been approved in Europe.

To give you some idea of how large the market is for ED treatment, consider Pfizer (NYSE:PFE) raked in some $1.7 billion in Viagra sales last year. The newcomers won't have an easy time gaining market share, however; Pfizer has heavily promoted its little blue pill to the estimated 30 million American men with some degree of impotence, making Viagra one of the most recognizable brand names in the U.S. But here's the kicker: About 90% of those 30 million have not yet sought treatment.

Are there any differences in the three products? It's hard to say because there have been no head-to-head tests. We know that all three work by blocking the same enzyme, and all three are pills (though Viagra is blue, Levitra is orange, and Cialis is yellow). The three do have some different properties, however. Perhaps the biggest distinction belongs to Cialis, which its marketers claim is effective for up to 36 hours -- or about five to seven times longer than the other two.

One last difference: Bayer and GlaxoSmithKline have tabbed tough guy and former NFL coach Mike Ditka as their Levitra spokesman. Even though he's about twice the age of Viagra pitchman and Rangers first baseman Rafael Palmeiro, "Coach Ditka" could back Palmeiro down with just a scowl.

Look for a ton of advertising as this battle escalates... coming soon to a television near you.

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